docs: def on_delete(self, node):    # ('targets',)
          """Delete statement."""
          for tnode in node.targets:
              if tnode.ctx.__class__ != ast.Del:
                  break
              children = []
              while tnode.__class__ == ast.Attribute:
                  children.append(tnode.attr)
                  tnode = tnode.value
  
              if tnode.__class__ == ast.Name and tnode.id not in self.readonly_symbols:
                  children.append(tnode.id)
                  children.reverse()
                  self.symtable.pop('.'.join(children))
              else:
                  msg = "could not delete symbol"
                  self.raise_exception(node, msg=msg)